Evol Ecol Res 10: 333-350 (2008)     Full PDF if your library subscribes.

Measuring the population-level consequences of predator-induced prey movement

Peter A. Abrams*

Department of Ecology and Evolutionary Biology, Zoology Building, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada

e-mail: abrams@zoo.utoronto.ca


Questions: (1) What impact does adaptive movement away from areas of high predation risk have on the dynamics of a prey species and its resource? (2) What can experiments that introduce or remove predator cues tell us about the answer to question (1)?

Mathematical methods: These questions are addressed using a two-patch meta-community model in which predators and/or their cues are incorporated into a system consisting of a prey species and its resource. Predators and/or cues may be introduced to one or both patches.

Key assumptions: Prey species move adaptively to maximize their instantaneous rate of increase, but also make some random movement. Predators move randomly or do not move. Resources seldom or never move between patches. Consumer species have saturating functional responses.

Conclusions: (1) Adaptive movement can stabilize or destabilize the dynamics of the tri-trophic system. (2) Monitoring densities in a single patch may give a misleading indication of the global change in densities. (3) Adaptive prey movement in response to predator cues may increase or decrease prey density. (4) Predator introduction may cause an increase or decrease in the size of the prey population. (5) Short-term experiments with local measurements may greatly overestimate the impact of predators on prey and the behavioural component of that impact. (6) The dynamics and interspecific effects in a system with predators and adaptive avoidance by prey cannot in general be deduced from separate experiments with cues alone and with predators in the absence of the cues. (7) Conclusions from recent empirical studies should be reassessed in light of these results.

Keywords: functional response, habitat selection, meta-community, non-consumptive effect, predator–prey interaction, trait-mediated indirect interaction, tri-trophic system.

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